I. Facial Bones
A. Maxillary Bones
B. Zygomatic Bones
C. Lacrimal Bones
D. Nasal Bones
E. Inferior Nasal Conchae
F. Palatine Bones
II. Bony Nasal Septum
III. Nasal Fossae
VI. Paranasal Sinuses
VII. CT Images
A. Exam 1
1. Coronal Images
2. Axial Images
B. Exam 2
1. Coronal Images
2. Axial Images
VIII. Review Questions
68 Fundamentals of Sectional Anatomy
FACIAL BONES Maxillary Bones
Chapter 1 presented the eight cranial bones: the frontal, The two maxillary bones are the largest immovable
two parietals, occipital, two temporals, sphenoid, and eth- bones of the face and are solidly united midline inferiorly.
moid. In examining CT images for facial bones you again They are involved in forming three cavities: the oral, nasal,
encounter some of these same bones as well as the 14 and orbital. The upper teeth are imbedded in the inferior
facial bones themselves. The list of facial bones includes margin, the alveolar process or alveolar ridge. Figure
the two maxillae, two zygomatic bones, two lacrimal bones, 2-1 demonstrates the maxillary bones from an anterior per-
two nasal bones, two nasal conchae, two palatine bones, spective, including the frontal processes articulating with
one vomer, and one mandible. the frontal bone. Figure 2-2 shows the inferior horizontal
portion of the maxillary bone, the palatine process. It forms
the anterior part of the hard palate, or roof of the mouth.
Frontal bone Parietal bone
Temporal bone Frontal process
of maxillary bone
Sphenoid bone Nasal bone
Middle nasal concha
of the ethmoid bone Inferior nasal concha
Alveolar process of maxillary bone
Alveolar process of mandible
Mentum of mandible
Figure 2-1 External frontal view of facial bones
CHAPTER 2 Face 69
Zygomatic Bones Nasal Bones
The two zygomatic or malar bones form the promi- The two nasal bones are fused midline and form the
nent part of our “cheek bones” and are seen on Figure 2-1. bridge of the nose as seen on Figure 2-1.
The zygomatic bones have three points of attachment:
anteriorly with the maxillary bone, superiorly with the Inferior Nasal Conchae
frontal bone, and posteriorly with the temporal bone. Also demonstrated on Figure 2-1 are the two inferior nasal
Trauma may cause them to become free-floating, an injury conchae, or turbinates, which are separate facial bones.
called a “tripod” fracture.
Lacrimal Bones Forming the posterior part of the hard palate are the
The two lacrimal bones, also seen on Figure 2-1, are two palatine bones. On Figure 2-2, they are seen pos-
very tiny bones that help form the medial wall of the terior to the palatine processes of the maxilla. The palatine
orbits. They are difficult to distinguish on CT images bones have vertical portions that extend superiorly and are
because of their size. minimally involved in forming the orbit.
palate of maxilla
Figure 2-2 External view of inferior skull
70 Fundamentals of Sectional Anatomy
Vomer the mandible from an anterior perspective and Figure 2-4
The vomer forms the inferior part of the bony nasal demonstrates it from a lateral perspective. The lower teeth
septum while the perpendicular plate of the ethmoid bone are rooted in the alveolar ridge or process of the mandible.
forms the superior segment. Their relationship is shown on The inferior tip of the mandible is the chin or mentum
Figures 2-1 and 2-3. and is identified on Figures 2-1 and 2-4. Also seen on
Figure 2-4 is one of the bilateral condyloid processes of
the mandible. These processes articulate with the temper-
Mandible omandibular fossae of the temporal bones to form the
The mandible is the largest facial bone and the only temporomandibular joints.
movable bone in the adult skull. Figure 2-1 demonstrates
Frontal bone Ethmoid
Palatine process of sphenoid bone
Horizontal plate Perpendicular plate
of palatine bone of palatine bone
Figure 2-3 Midsagittal view of bony nasal septum
CHAPTER 2 Face 71
Nasal bone Occipital bone
Lacrimal bone Temporomandibular
Condyloid process meatus
Maxilla Mastoid process of
Alveolar process Styloid process
Alveolar process of maxillary bone
Mentum of mandible Mandible
Figure 2-4 External lateral view of facial bones
72 Fundamentals of Sectional Anatomy
BONY NASAL SEPTUM sagittal line drawing of the nasal septum, and you see both
the perpendicular plate of the ethmoid bone and the
The nasal septum, the partition separating the two nasal vomer. When studying coronal CT images, the perpendi-
fossae, is cartilaginous anteriorly and bony posteriorly. The cular plate of the ethmoid bone is easily differentiated
bony nasal septum is actually composed of two separate from the vomer. The separate components of the bony
pieces of bone. Superiorly it is formed by the perpendi- nasal septum are more difficult to identify on axial CT
cular plate of the ethmoid bone, as pictured from an images. Also easily identified on CT coronal images are the
anterior perspective on Figure 2-5. Figure 2-6 places the cribiform plate, the horizontal superior portion of the
ethmoid bone with respect to the orbits and nasal cavity. ethmoid bone, and the crista galli, the small superior
The inferior portion of the bony nasal septum is a separate extension off the cribiform plate. Figures 2-3, 2-5, and 2-6
facial bone, the vomer. Look back at Figure 2-3, a mid- show these structures.
air cells mass
Figure 2-5 Frontal view of ethmoid bone
Crista galli Cribriform plate
Figure 2-6 Ethmoid bone in place
CHAPTER 2 Face 73
NASAL FOSSAE bone. All are visible on Figure 2-7. The orbit is conical in
shape, as shown on Figure 2-8, with the widest portion, the
The nasal fossae, cavities found on either side of the nasal
base, being located anteriorly. When doing coronal CT
septum, are broken into compartments by smaller scroll-
images, it becomes increasingly smaller as one cuts pos-
like bones called conchae or turbinates. There are three
teriorly. If someone receives a direct hit in the region of
pairs of conchae or turbinates, the superior, middle, and
the orbit, the orbit will give in the weakest region, the
inferior. The superior and middle conchae are medial
floor. This would be termed a “blow-out” fracture.
extensions off the two lateral masses of the ethmoid bone.
The inferior conchae are separate facial bones. The func-
tion of the conchae is to separate the nasal cavity into
smaller compartments. When air is inhaled, it is forced to
travel through the compartments, and is warmed, filtered Frontal
by the cilia, and moistened by the mucous membranes lin- Sphenoid
ing the nasal cavity. From a coronal perspective, the infe- bone
rior and middle conchae are visible on CT images. The Malar
superior conchae are much smaller and may not always be Ethmoid (zygomatic)
identifiable. Figure 2-1 labels the conchae. bone bone
There are seven bones involved in forming the orbit. The
roof of the orbit is formed by the horizontal portion of the Maxilla
frontal bone. The floor is formed by the maxillary bone
along the medial aspect and the zygomatic bone along the
lateral aspect. The medial wall is formed by the ethmoid
and lacrimal bones. The lateral wall is formed by the zygo-
matic bone and posterolaterally by the sphenoid bone.
Minimally involved is the vertical portion of the palatine Figure 2-7 The bones of the orbit
Figure 2-8 The orbits
74 Fundamentals of Sectional Anatomy
EYE ity exiting the back of the eye. The lens of the eye is also
visible on sagittal and axial CT images, but should not be
Certain muscles are involved in moving the eye. Those evi-
confused with the optic nerve on coronal images, as it is
dent on CT images are the superior, inferior, medial (or
not visible. It is transparent and convex, allowing light to
internal), and lateral (or external) rectus muscles. From a
reach the retina, but at the same time causing refraction of
coronal perspective you see all four; from an axial per-
light. Figure 2-9 demonstrates the medial and lateral rec-
spective you see the medial and lateral muscles; and from
tus muscles, optic nerve, retina, and lens while Figure 2-10
a sagittal perspective you see the superior and inferior. The
shows three of the four rectus muscles.
retina is the innermost layer in the posterior eye that con-
tains the rods and cones, the nerve cells responsible for
vision. The optic nerve exits through the optic foramen in
the posterior orbit carrying the sensory information PARANASAL SINUSES
received by the retina. The optic nerve is seen on coronal The paranasal or accessory nasal sinuses are air-filled
CT images as an area of opacity in the center of the eye. cavities located in some cranial and facial bones. They
Looking at axial images, it is visible as a linear area of opac- communicate with the nasal cavity and with each other.
Lateral rectus muscle
Medial rectus muscle
Figure 2-9 Transverse view of the eye
Inferior Inferior Lateral
oblique rectus rectus
Figure 2-10 The muscles of the eye
CHAPTER 2 Face 75
Their function is to lighten the head and add resonance to The sphenoid sinuses are beneath the sella turcica, in the
the voice. They are lined with mucous membranes and with body of the sphenoid bone. A septum separates the sphe-
pathology can become filled with fluid. Named for the noid sinus from the ethmoid sinuses and an additional
bones in which they are located, they are the maxillary, septum exists if there is more than one sphenoid sinus.
frontal, ethmoid, and sphenoid. Only the maxillary The sphenoid sinuses are located posterior to the ethmoid
sinuses are present at birth. The frontal and sphenoids sinuses, as drawn on Figure 2-11. The frontal sinuses
form around the age of 6 or 7, and the last to develop, are the most superior and the maxillary sinuses the most
in the late teens, are the ethmoids. The largest are the inferior. Coronal CT images demonstrate that the frontal
maxillary sinuses, with one being located in the body of sinuses are the most anterior and the sphenoid sinuses
each of the two maxillary bones. The frontal sinuses are in the most posterior. If the orbits are visible on coronal
the vertical portion of the frontal bone. There may be cuts, the sinuses you are visualizing are probably the eth-
either one or two, with a septum or wall dividing them if moids rather than sphenoids. Figure 2-12 demonstrates
two exist. Rarely are they symmetric. The many ethmoid all four paranasal sinuses from a coronal perspective. The
sinuses are located within the two lateral masses of the sinuses appear translucent on CT images unless pathology
ethmoid bone, found along the medial wall of each orbit. exists.
Figure 2-11 Lateral view of paranasal sinuses
air cells Sphenoid
Figure 2-12 Frontal view of paranasal sinuses
76 Fundamentals of Sectional Anatomy
of ethmoid bone Nasal
Figure 2-13 Although Figure 2-13 is not the first image of this exam, it is anterior enough to demonstrate the
unusually large but typical asymmetric frontal sinuses.The nasal bones are seen along with the portions of the maxillary
bones involved in forming the medial walls of the orbits, the frontal processes. Just starting to appear is the perpen-
dicular plate of the ethmoid bone which forms the superior portion of the bony nasal septum.
Superior orbital sinus
plate of ethmoid
Figure 2-14 The superior orbital margin, formed by the frontal bone, is evident on Figure 2-14. More of the per-
pendicular plate of the ethmoid bone has appeared. The lower edge of the maxillary bone, the alveolar process, is
shown. It is here that the upper teeth attach.The lacrimal bones, which help to make up the medial walls of the orbits,
CHAPTER 2 Face 77
Cribiform plate orbital
of ethmoid bone margin
Ethmoidal air Lateral mass of
cells ethmoid bone
Middle nasal Zygoma
Maxillary bone Inferior
Figure 2-15 Clearly seen on Figure 2-15 is the crista galli extending superiorly from the cribiform plate of the
ethmoid bone. Some of the many ethmoidal air cells, found in the lateral mass of the ethmoid bone, have become
visible. In addition to the lacrimal bones, the lateral masses of the ethmoid bone help form the medial walls of the
orbits. Just starting to appear are the largest of the sinuses, the maxillary sinuses, in the bodies of the maxillary bones.
Figure 2-15 also shows the midpoint of the mandible, the mentum, as well as the inferior and middle conchae or
turbinates. The inferior conchae, separate facial bones, and the superior and middle conchae extending medially from
the lateral masses of the ethmoid bone divide the nasal cavities into compartments. The vomer is seen forming
the inferior part of the bony nasal septum. Notice the role the nasal maxillary bones assume in forming the inferior
Ethmoid Superior orbital margin
sinus (frontal bone)
Lateral mass Crista galli
of ethmoid bone
Maxillary sinus Inferior
Figure 2-16 Figure 2-16 demonstrates the cribiform plate of the ethmoid bone along with the crista galli.
The zygomatic or malar bones are prominent and their involvement in forming the lateral walls of the orbits can be
78 Fundamentals of Sectional Anatomy
Superior rectus nerve
Medial rectus rectus
Inferior rectus Maxillary
Figure 2-17 On Figure 2-17, the maxillary sinuses are fully demonstrated, for the most part nonpathologic except
for a small area of opacity in the lower right maxillary sinus. A small part of the upper mandible is just starting to
appear. Also seen on this coronal image are the four rectus muscles (superior, inferior, lateral, and medial), along with
the optic nerve.
of ethmoid bone
Middle nasal Maxillary
Figure 2-18 Notice the diminished size of the orbits on Figure 2-18, an indication that the image is posterior.
The sphenoid bone is seen making up the posterolateral walls of the orbits.
CHAPTER 2 Face 79
Body of clinoid
Figure 2-19 This last coronal image of Exam 1, Figure 2-19, shows the anterior clinoids of the sphenoid bone along
with the sphenoid sinuses, found in the body of the sphenoid bone. Little of the maxillary sinuses remain to be seen
this far posteriorly.
Figure 2-20 This first axial image of Exam 1, Figure 2-20, demonstrates the frontal sinuses within the frontal bone. It
also shows the unique construction of the cranial bones with diploe sandwiched between two layers of compact bone.
80 Fundamentals of Sectional Anatomy
Roof of orbit
of frontal bone
Figure 2-21 Figure 2-21 shows how the roof of the orbits is formed by the horizontal portion of the frontal bone.
Figure 2-22 On Figure 2-22, the lateral masses of the ethmoid bone are involved in forming the medial walls of
CHAPTER 2 Face 81
plate of ethmoid
Lens of eye bone
Ethmoidal air Medial rectus
Optic nerve Lateral rectus
Figure 2-23 Seen on Figure 2-23 are the small, numerous, ethmoidal air cells found in the lateral masses or
labrynths of the ethmoid bone. Identified are the nasal bones, as well as the perpendicular plate of the ethmoid bone
forming the superior portion of the bony nasal septum. Although faintly visible, you can distinguish the medial and
lateral rectus muscles, optic nerve, and lens of the eye.
Bony nasal Lacrimal
Zygoma air cells
Figure 2-24 The bony nasal septum separates the two nasal fossae on Figure 2-24. Between the two orbits are
the ethmoidal sinuses. Helping to form the medial walls of the orbits are the two lacrimal bones.The zygoma, involved
in forming the lateral walls of the orbits, is shown.
82 Fundamentals of Sectional Anatomy
Figure 2-25 Appearing for the first time in this series of images on Figure 2-25 are the maxillary sinuses and the
maxillary bones. Also distinguishable are the sphenoidal sinuses, located in the body of the sphenoid bone beneath
the sella turcica. On either side of the bony nasal septum are the conchae or turbinates.The prominent zygoma is seen
Figure 2-26 On Figure 2-26, compare the size of the maxillary sinuses, the largest and the only ones present at
birth, to the frontal, ethmoidal, and sphenoidal sinuses. In the mastoid region of the temporal bones are the mastoid
CHAPTER 2 Face 83
Figure 2-27 Figure 2-27 is at a lower level of the maxillary sinuses.
Figure 2-28 Figure 2-28, a thinner interslice gap compared to the previous images, is included because it demon-
strates the hard palate. The hard palate or roof of the mouth is composed of the palatine processes (the horizontal
portion of the maxillary bone) anteriorly and the two palatine bones posteriorly. Both should be united midline.
84 Fundamentals of Sectional Anatomy
Figure 2-29 This last slice of Exam 1, Figure 2-29, shows the mandible, along with the alveolar process of the max-
illary bones where the teeth insert.
CHAPTER 2 Face 85
Frontal Nasal bone
Figure 2-30 Seen on Figure 2-30 are the frontal sinuses within the frontal bone, the union of the frontal bone
with the frontal processes of the maxillary bones, the nasal bones, and the perpendicular plate of the ethmoid bone.
orbital Cribiform plate
Ethmoidal of ethmoid
Figure 2-31 On Figure 2-31, the lateral masses of the ethmoid bone descending from the cribiform plate form
the medial walls of the orbits. Extending superiorly from the cribiform plate is the crista galli and within the lateral
masses are the ethmoid sinuses.The maxillary bones are just becoming visible.The superior orbital margin is formed
by the frontal bone.
86 Fundamentals of Sectional Anatomy
Figure 2-32 The inferior orbital margins are shown on Figure 2-32 formed by the maxillary bones medially and
the two zygomatic bones laterally. The upper teeth are imbedded in the alveolar process of the maxillary bone. Just
starting to appear are the maxillary sinuses.
Lateral rectus Optic nerve
Ethmoidal air sinus
concha Zygomatic (malar)
sinus Middle nasal
Vomer Inferior nasal
Figure 2-33 On Figure 2-33 the conchae are seen dividing the nasal fossae into compartments. The size of the
maxillary sinuses is appreciated. The vomer, making up the lower bony nasal septum, is identified as is the zygomatic
prominence forming the cheeks bilaterally. Lastly, notice the rectus muscles and optic nerve.
CHAPTER 2 Face 87
Figure 2-34 Figure 2-34 has labeled the mentum or midpoint of the chin.
Figure 2-35 On Figure 2-35, the nasal septum separates the two nasal fossae while the conchae divide them into
88 Fundamentals of Sectional Anatomy
Figure 2-36 The anterior clinoids of the sphenoid bone are seen on Figure 2-36 along with the sphenoid sinuses
in the body of the sphenoid bone beneath the sella turcica.
Medial and sinus
Figure 2-37 Figure 2-37 shows the sphenoid sinuses as well as the medial and lateral pterygoid processes of the
CHAPTER 2 Face 89
air cells Temperomandibular
process of mandible
Figure 2-38 Figure 2-38, the last image in this series, is a larger interslice gap compared to the previous images
but is included to demonstrate the condyloid processes of the mandible articulating with the temporomandibular
fossae of the temporal bones comprising the temporomandibular joints.
Figure 2-39 On Figure 2-39 you see the horizontal portion of the frontal bone forming the roof of the orbits.
The frontal sinuses within the squamous portion of the frontal bone are also identified.
90 Fundamentals of Sectional Anatomy
Lateral of orbit
Posterior clinoid of
clinoid of sphenoid
Figure 2-40 Figure 2-40 demonstrates the medial and lateral walls of the orbits taking shape. The anterior and
posterior clinoids of the sphenoid bone are shown.
Lacrimal bone Ethmoid air
Lateral mass of
plate of ethmoid
Figure 2-41 On Figure 2-41, the ethmoid and sphenoid sinuses are seen. Also identified is the medial wall of the
orbit, formed by the lateral masses of the ethmoid bone and by the lacrimal bones. Labeled is the perpendicular plate
of the ethmoid bone forming the superior portion of the bony nasal septum. Notice the medial and lateral rectus
muscles and the mastoid air cells.
CHAPTER 2 Face 91
bone Lens of
Figure 2-42 Three of the four sinuses are seen on Figure 2-42: the maxillary, sphenoid, and ethmoid. All com-
municate with the nasal cavity. Also seen are the lens of the eyes and the nasal bones.
magnum Mastoid air
Figure 2-43 Still apparent on Figure 2-43 are the nasal bones but more obvious now is the zygoma.The foramen
magnum is seen along with the mastoid region of the temporal bones containing the mastoid air cells.
92 Fundamentals of Sectional Anatomy
Figure 2-44 Demonstrated on Figure 2-44 is the inferior bony nasal septum formed by the vomer. The fully
formed maxillary sinuses are also seen.
of hard palate
Figure 2-45 Figure 2-45, the last image shown in this exam, is a bigger interslice gap than the preceding images but
is included to demonstrate the palatine process of the hard palate.
CHAPTER 2 Face 93
REVIEW QUESTIONS 10. Which of the following imaging planes will not
demonstrate the lens of the eye?
1. The superior, middle, and inferior turbinates are part a. Coronal
of the lateral masses of the ethmoid bone. b. Axial
a. True c. Sagittal
b. False d. They all will demonstrate the lens of the eye.
2. Which bone ends up disassociated in a tripod fracture? 11. On which imaging plane would you be able to see all
a. Frontal four rectus muscles of the eye?
b. Zygoma a. Sagittal
c. Temporal b. Coronal
d. Maxilla c. Axial
d. All would be visible on all imaging planes.
3. Which bone forms the superior portion of the bony
nasal septum? 12. Which paranasal sinus would appear first on CT
a. Ethmoid images of the face done in a coronal plane arranged
b. Sphenoid from anterior to posterior?
c. Vomer a. Ethmoid
d. Frontal bone b. Maxillary
4. What is the function of the conchae or turbinates in
the nasal cavity?
13. The largest of the paranasal sinuses are the
Match the different portions of the orbit with the bones c. sphenoid.
composing them. d. maxillary.
5. Roof a. Maxillary, zygoma 14. The first paranasal sinuses to develop are the
6. Floor b. Ethmoid, lacrimal
7. Medial wall c. Zygoma, sphenoid c. maxillary.
8. Lateral wall d. Frontal bone
15. The function of the paranasal sinuses is
9. Which part of the orbit is involved in a blowout frac-
a. Roof .
b. Lateral wall
c. Medial wall